1. Field of the Invention
The present invention relates generally to lens modules and, more particularly, to a lens module having a variable focus and to a camera module using the lens module.
2. Description of related art
With the development of wireless communication technologies, increasing numbers of mobile phones and PDAs now include digital cameras as a special feature.
Generally speaking, digital cameras are image-recording media capable of photographing images without using film. Such a digital camera typically uses an image pickup device, which is a kind of semiconductor device, such as a charged coupled device (CCD) or complementary metal oxide semiconductor (CMOS). In the digital camera, an object image formed on the image pickup device through a lens is converted into an electronic signal by the image pickup device, and the electrical signal is stored as a digital signal, for example, either in the camera unit or in a mobile phone or PDA in which the digital camera is mounted.
Since the digital camera is to be mounted in a small mobile phone or PDA, a fixed focus lens module is usually used to facilitate mounting thereof. However, images photographed by a digital camera module with a fixed focus lens module tend to be of poor quality. This poor quality is partly due to the fixed focus lens system, which is incapable of adjusting a distance between the lens(es) and the image pickup device and/or between the lenses themselves to make a clearer image when photographing objects at different distances from the camera. Thus, a focusing structure or a zoom structure is required to change the focus of the digital camera module.
A typical driving apparatus uses a gear or cam mechanism to realize the focusing or zoom function. This structure is relatively large and makes the camera structure fairly complicated. Furthermore, the operation of the mechanical structure consumes a substantial amount of energy, which is of concern given the limited battery capacity of the portable device with which it is associated. In addition, the precision of the mechanical transmission is not high.
Therefore, a new lens module is desired in order to overcome the above-described shortcomings.